1. Field of the Invention
The present invention is directed to a method for generating and checking a security impression arrangement for implementing the method.
The invention is particularly directed to postage meter machines that deliver a completely electronically produced impression for franking postal matter including the printing of an advertising slogan and a mark. The postage meter machine is equipped with at least one input means, an output means, and input/output control module, memory means, control means and a printer module.
2. Description of the Prior Art
A postage meter machine usually produces an impression at the flush right, parallel to the upper edge of postal matter in a form agreed upon with the post office, beginning with the content of the postage value in the franking, the data in the postmark and impressions for advertising slogan, and possibly an identification of the type of mailing in the selective impression. The postage value, the date and the type of mailing form variable information which is to be entered according to the item mailed.
The postage value is usually the delivery fee (franking) prepaid by the sender that is taken from a refillable credit register and is employed for prepaying the mailing.
The date is the current date, or a future date in a postmark. Whereas the current date is automatically offered by a clock/date module, a setting of a desired future date must be undertaken by a manual pre-dating. Pre-dating is of interest in all instances wherein the volume of postal matter must be handled and franked in an extremely timely fashion but must be sent by a specific deadline. Embedding the variable data for the date in the postmark can be fundamentally undertaken in the same way as the impression of the postage value.
The approved advertising slogans can contain a large variety of types of messages, particularly the address, the company logo, the post office box and/or any other desired message. The advertising slogan is an additional inclusion that must be agreed upon with the postal authorities.
U.S. Pat. No. 4,580,144 discloses an electronic franking unit having two thermal printing devices, whereby the fixed part of the print format (postal authority mark and image frame) is printed by the first device and the variable part of the print format (postage and date) is printed by the second device, the parts being printed in succession. The printing speed can be increased as a result of this division and separate handling of the variable and constant data. A security impression, however, is not created, however, because of the lack of a "fingerprint".
German OS 38 23 719 discloses a security system having a character printing authorization means. A computer in the postage meter machine has a memory into which data for a modification in graphics can be loaded and which also contains data corresponding to the date allocated to the modification. When the user requests a change in financial resources, the computer of the postage meter machine accesses an external dialing means via a connecting device (modem) that undertakes a selection of a character pattern to be printed. A disadvantage of this known system is that the user of the postage meter machine is not given any freedom for selecting the character pattern. The printed character pattern is employed for checking the security of the authorization of the postage meter machine. The entire, printed print format including that special character pattern must be evaluated by the postal authority, which is possible only with high outlay.
It has been proposed to apply certain hidden or encoded characters, barcodes, in the postage machine impression on the postal matter with a plurality of printer heads as visible or invisible marks in order to be able to identify forgeries.
The apparatus disclosed in U.S. Pat. No. 4,775,246, thus, an alphanumerical number is additionally printed in the postmark and, in the apparatus disclosed in U.S. Pat. No. 4,649,266, an individual, alphanumerical digit is additionally co-printed in a number in the postmark, but subjective errors are not precluded when post office employees compare such digits or numbers. U.S. Pat. No. 4,934,846, by contrast, discloses a machine-readable barcode printed in a separate field next to the impression of the postage value; this, however, disadvantageously diminishes the available printing area for the postmark and/or for the advertising slogan.
Applying such a barcode with a separate printer is disclosed in U.S. Pat. No. 4,660,221 and in U.S. Pat. No. 4,829,565, whereby a character having transposed or offset elements is also printed in the latter patent, the mismatch or offset thereof containing the relevant security information. The printer device is supplied in alternation with variable data from a memory means and with data from an encoding circuit, by a selection means. Alphanumerical characters having regions (speckles) mixed therein are produced in the field provided for the variable data and are printed on the print medium. According to U.S. Pat. No. 4,641,346, the evaluation ensues by reading such a character column-by-column and making a column-by-column comparison with stored characters in order to reacquire the security information. The data derived from the encoding circuit are thereby in turn separated, a further means being required for this purpose. The evaluation is correspondingly complicated and can only be accomplished with complicated apparatus and with qualified postal employees.
Since the presentation of relevant information in the form of a barcode requires a relatively large amount of space, a two-dimensional barcode has likewise been proposed. A remaining disadvantage, however, is that barcodes can only be machine-checked, i.e. they cannot be additionally manually checked. A security system disclosed in U.S. Pat. No. 4,949,381 employs imprints in the form of bitmaps in a separate marking field under the imprint of the postage meter machine. Even though the bitmaps are especially tightly packed, the height of the stamped image is reduced by the height of the marking field due to the size of the marking field that is still required. Too much of the area required for an advertising slogan is thus lost. The high-resolution recognition means required for evaluating the mark is also disadvantageous.
Another security system employs imprints in the form of a diagram (U.S. Pat. No. 5,075,862) within the stamped imprint of the postage meter machine. When, however, individual printer elements are down, dots in the print format are missing, this potentially leading to a signaling of an alleged forgery. Such marks in diagram form within the stamped impression of the postage meter machine are therefore not reliable. Even given a faultless impression, the machine reading is made more difficult since the entire print format must always be evaluated.
Further, German OS 40 03 006 discloses a method for analyzing the printed impression postal matter in order to enable an identification of the postage meter machine, which made the impression whereby a multi-place cryptographic number is formed incorporating the date, machine parameters, the postage value and the advertising slogan, and is separately intermediately stored. The cryptographic number is additionally inserted into the printed pattern during printing via a printer control that sets the printer means. A forgery or any imitation of the stamp of the postage meter machine by an impression of a postage value that has not been accounted for can be recognized based on the cryptographic number. That user who manipulated the postage value can easily be detected even given a plurality of users of a single postage meter machine. This approach, however, does not permit the use of a fully electronically produced print format for an impact-less printer, nor can such a print format be electronically evaluated in a simple way.
For security-orientated reasons, it has been proposed in German OS 40 34 292, in a fully electronically produced print format, to store only a constant part of the franking image in the postage meter machine and to send the other, associated variable part to the postage meter machine from the central data station in order to compose the ultimate print format. The fully electronically produced advertising slogan in this solution, however, likewise forms part of the constant data of the franking image, as does the frame arrangement of the value and the postmark with an indication of locating and, possibly, the zip code.
A communication of the terminal equipment containing a franking module with a central data station is thus necessary for compiling the print data for every franking. The printing is thereby delayed, making this solution unsuitable for bulk franking of a large quantity of postal matter.
In a postage meter machine disclosed in U.S. Pat. No. 4,746,234, fixed and variable data sets are stored in memory means (ROM, RAM), the date being read out with a microprocessor when a letter actuates a microswitch on the conveying path preceding the printing position and in order to form a print control signal. These two data sets are subsequently electronically combined for form a print format and can be printed out with a thermal printing means on an envelope to be franked. Given a large number of variable data, the formation of the print control signal is correspondingly delayed. The maximum printing speed that can be achieved given unaltered postal data is limited, in particular, by the time required in the formation of the print control signal. An additional material outlay would have to be expended or the reduction of the printing speed would have to be accepted when a cryptographic number is to be calculated from the data in order to generate a mark for a security imprint therefrom. In both instances, lack of acceptance by customers must ultimately be anticipated for such a machine (high price and/or too slow).
The advantage of such a mark is that a franking stamp printed by a postage meter machine cannot be altered by a manipulator without a corresponding alteration of the mark, since a franking stamp modified with fraudulent intent, resulting in an inapplicable mark, can be recognized. It would still be necessary, however, to identify the manipulated postage meter machine whose function had been tampered with.
U.S. Pat. No. 4,812,965 discloses a remote inspection system for postage meter machines that is based on specific messages in the imprint on mailings that must be sent to the central data station. Sensors within the postage meter machine are intended to detect any falsification action that was undertaken so that a flag can be set in designated memories if the postage meter machine is tampered with for manipulative purposes. Such tampering could ensue in order to load an unpaid credit into the register. A disadvantage, such a system cannot prevent a knowledgeable manipulator who breaks into the postage meter machine from subsequently eliminating evidence of the tampering, by erasing the flags. Further, this cannot prevent the imprint itself from being manipulated, even though it is produced by a properly operated machine. There is the possibility in known machines of producing imprints with the postage value of zero. Such zero frankings are required for testing purposes and could be falsified in that a postage value greater than zero is simulated.